The emergence of the theory and method of architectural restoration in Leningrad is usually attributed to the post-war period, but the pre-revolutionary experience of the restoration of monuments is known too. The restoration in Leningrad in the 1920s - 1930s and the question of the continuity of pre-war and post-war restoration in the city remain unexplored. The purpose of the article is to examine the history of restoration in Leningrad at the personal and methodological levels from pre-revolutionary to post-war times in the ideological context of the 1910s - 1940s. The main sources of the article were unpublished documents from seven Petersburg’s archives. The analysis of these sources allowed the author to recreate the history of the gradual extinction of the school of architects-researchers that existed at the Academy of Arts. They aspired to a total scientific study of the monuments of Russian national architecture during the restoration work. Cooperation of the last representatives of this school - architects A.P Udalenkov (1887-1975) and N.P Nikitin (1884-1971) -with the Inspectorate for the Protection of Monuments and young restorers after the war ensured the continuity of theoretical positions and practical methods of architectural restoration from the Petrograd academic school to the so-called “Leningrad school”. However, the ideological basis of the work of architects-researchers, convinced of the originality of national architecture and the need to preserve the monuments of Russian art, was forgotten after the beginning of the “Leningrad affair”.